They stand like surreal monuments in the California scrubland: prototypes of Donald Trump's proposed "big, beautiful" border wall between the US and Mexico.
The eight 30ft high slabs are the first tangible part of the controversial project that the US President says will help solve America's immigration problems.
Eight construction companies were given the chance to produce their example of a wall that would work.
Officials from Customs and Border Protection (CBP) are now testing those offerings.
The wall was one of Mr Trump's dominant campaign promises but few believe building it along 2,000 miles of border is realistic or feasible.
However, the CBP, which would have responsibility for the wall, says its existence sends a psychological message.
"The attention that these prototypes have brought to a worldwide audience has given us the ability to send the message," said CBP division chief Mario Villarreal.
"The message that we're a wonderful country, the greatest country in the world, and to those who want to come to the United States we highly recommend that they choose legal methods."
But opponents of the wall say it sends a very different message.
Enrique Morones has run Border Angels since the 1980s, advocating for human rights and humane immigration reform.
He said: "Without a doubt, it is a wall of hate. It tells the world, 'Do as I say, not as I do.'
"We know that the majority of the population of the United States is against the wall. There isn't the money for it, it is just for show."
US officials say the building of the existing physical barrier between the US and Mexico in the San Diego area has slashed the numbers trying to cross illegally.
In 1986, 628,000 people were apprehended making the attempt. Last year it was just 31,000.
But campaigners say the result of people trying to find alternative routes has been an increase in deaths among would-be migrants.
At San Diego's Friendship Park, families divided by the border regularly meet on either side to talk through the fence.
Recently, for only the sixth time ever, officials opened a gate in the fence to allow a few families to reunite briefly.
Brian Houston and Evelia Reyes used their three minutes together to get married.
Brian said: "We were very fortunate to be reunited and show that love has no borders. I wish the fence wasn't there.
"I think it is really sad, it is dividing families, dividing people, I don't understand the reasons for it."
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